Influence of wind and temperature on the height limit of a radio acoustic sounding system

Abstract

Influences of the atmospheric wind and temperature profiles upon the maximum height in temperature measurement by using a radio acoustic sounding system (RASS) were studied. The RASS uses radar to receive echoes (RASS echoes) backscattered from periodic perturbations in the atmospheric refractive index produced by an incident acoustic pulse and to measure the atmospheric temperature from the local speed of sound which is derived from the Doppler frequency shift of the RASS echo signal. One of the important conditions for the RASS echo to be efficiently backscattered (for monostatic radar) is that the radar beam is incident normal to the wave surface of the perturbations in the refractive index, i.e., to the acoustic wave front. This paper gives the results from numerical calculations to simulate the portion of the acoustic wave front where the above condition is satisfied, under a fixed configuration of the radar and acoustic antennas, and under changing shapes of the propagating acoustic pulse wave front influenced by height‐varying background atmospheric wind and temperature. Comparisons between the calculations and RASS experiments were made by using the middle and upper atmosphere (MU) radar with steerable beam under different atmospheric conditions. The numerical estimations of the height range for effective reception of RASS echo agree quite well with actual RASS observations carried out by using the MU radar. RASS echoes were obtained at altitudes up to 8.4 km under strong wind conditions in January 1988 and up to 22 km under calm wind conditions in July 1986.